The present invention relates to a molded resin plate formed with internal voids and extending like a two-dimensional plane or three-dimensional curved surface, and to a method and a system for manufacturing a molded resin plate.
The molded resin plate is a useful partitioning structural material employable with preference as an interior or exterior material for vehicles or an interior or wall material for buildings, for example.
As a partitioning structural material, the molded resin plate is generally required to be light in weight and to have an adequate strength for use.
The lightening of a molded resin plate can be achieved by that of the resin material, and by a reduction in quantity of resin to be used. However, the former has a limited number of choices in respect of material strength and cost, and the latter is relied on in most cases.
The lightening of a molded resin plate by a reduction in resin quantity in use is implemented by way of molding a plate body thinned entirely or reduced locally, and has involved problems as to the balancing with plate strength m for the moldability.
An entirely thin molded resin plate may have raised ribs or a honeycomb structure employed such as for an increased rigidity in sectional geometry, and may be laminated, as necessary for a desirable strength. However, the strength also is limited due to the thin body, besides the configuration in section that may need a die uneasy of production or uneasy temperature control, in addition to that the lamination provides a limited use due to an adhesive strength and a number of associated processes.
On the contrary, the lightening of a molded resin plate by a local reduction of plate body is implemented with a thick plate portion left between reduced wall portions, allowing a relatively high strength to be maintained. Therefore, if the flexibility of formation be kept outside the reduced wall portions, the production of dies should be facile, and if the reduction of plate body be possible in accordance with the use, the range of use as of a partitioning structural material would be spread as well, permitting a low-cost production of the molded resin plate.
There thus have been proposed molding methods in which a plate body is locally reduced by way of forming voids in the body of a molded resin plate.
In Japanese Parent Application Laid-open Publication 57-14968, there is proposed a method in which a cavity of an injection molding die is charged with a smaller amount of molted resin than a volume of the cavity, and the cavity is filled with a gas injected from a resin shot port, thereby forming a hollowed resin body.
In Japanese Patent Application Laid-open Publication 54-111557, there is proposed a method in which a die has a projecting piece formed on the interior for preventing an occurrence of a dent, and the temperature difference between a cavity region at the projecting piece side and the other cavity region is utilized to raise a reinforcing rib, which serves as a start point for a void to be formed in a molded body by injecting a gas, besides an additional disclosure in which a part of the die is slid to increase the cavity volume for formation of a reinforcing rib.
In Japanese Laid-on Parent Application publication 6-134828, there is proposed a method in which, along with an injection molding of such a rib structure, a check valve is employed for gas discharge therethrough to form a hollowed body. There is also shown a nozzle structure which has a check valve provided at a nozzle tip simply for forming an internal void. In Japanese Patent Application Laid-open Publication 6-155556, there is shown an arrangement having a heating device provided on such a nozzle tip. In Japanese Patent Application Laid-open Publication 8-276452, there is shown an arrangement in which a resin cylinder nozzle serves as a pressure medium discharge nozzle.
In Japanese Patent Application Laid-open Publication 5-131483, there is shown a mold having a connected void formed by gas discharge during an injection molding.
The prior arts described employ an effective molding system in which a fluid pressure medium serves in place of a solid core for forming a void in a body of a molded resin plate.
However, they substantially follow the conventional concept that the die should be clamped in position to have a cavity defined with an established volume for a body of resin to be injected therein for formation of a resin plate.
Therefore, developments of techniques are directed toward approximating the pressure medium to a core, holding down the fluidity of pressure medium, suppressing the flexibility in void formation, braking a diversity of developments for the molded resin plate to be light-weighted by reduction of plate body.
The present invention has been made with such points in view. It therefore is an object of the invention to provide a method and a system for manufacturing a molded resin plate formed with internal voids making use of the fluidity of pressure medium, increasing the flexibility in void formation, allowing a diversity of developments for the molded resin plate to be light-weighted by reduction of plate body. It also is an object of the invention to provide a molded resin plate formed with internal voids likewise allowing for a diversity of lightening measures.
An aspect of the invention to achieve the object is a method of manufacturing a molded resin plate formed with internal voids, comprising forming seed holes by discharging a pressure medium in a resin body injected in a cavity of a die, and increasing a size of the resin body, making the seed holes grow, by expanding the cavity of the die, supplying the pressure medium to the seed holes, to have a molded resin plate made of the resin body increased in the size and formed with the seed holes grown to internal voids.
According to this aspect, there is provided a method for manufacturing a molded resin plate with internal voids in which, by balancing pressures of a resin body and a pressure medium, internal voids of voluntary dimensions and configurations can be formed at voluntary locations, with an increased flexibility in void formation, with a maintained necessary strength, permitting diverse lightening measures to be promoted by way of a reduction of plate body.
Another aspect of the invention to achieve the object is a system for manufacturing a molded resin plate formed with internal voids, comprising a first molding wall and a second molding wall arranged in opposition to each other, a cavity defined by the first and second molding walls, a resin supply mechanism configured to supply the cavity with a body of a resin having a first volume, nozzles fitted to the first molding wall, a medium discharge mechanism configured to discharge a body of a pressure medium having a second volume under a pressure at a temperature, through the nozzles to the cavity, and a drive mechanism configured to move the second molding wall relative to the first molding wall to expand the cavity to a third volume equivalent to a sum of the first volume and the second volume under the pressure at the temperature. According to this aspect, there is provided a system for manufacturing a molded resin plate with internal voids in which, by balancing pressures of a resin body and a pressure medium, internal voids of controllable dimensions and configurations can be formed at locations corresponding to nozzles, with an increased flexibility in void formation, with a maintained necessary strength, permitting diverse lightening measures to be promoted by way of a reduction of plate body.
Another aspect of the invention to achieve the object is a system for manufacturing a molded resin plate formed with internal voids, comprising a die defining a cavity, a die drive system operative on the die to expand a size of the cavity, an injector configured to inject a resin body to the cavity, a resin supply system configured to supply the resin body to the injector, nozzles configured to discharge the pressure medium to the resin body injected in the cavity, a medium supply system configured to supply the pressure medium to The nozzles, and a controller which controls the die drive system, the resin supply system, and the medium supply system to form seed holes by discharging the pressure medium in the resin body injected in the cavity of the die and to increase a size of the resin body, making the seed holds grow, by expanding the cavity of the die, supplying the pressure medium to the seed holes, to have a molded resin plate made of the resin body increased in the size and formed with the seed holes grown to internal voids. According to this aspect, there is provided a system for manufacturing a molded resin plate with internal voids in which, by balancing pressures of a resin body and a pressure medium, internal voids of controlled dimensions and configurations can be formed at controlled locations, with an increased flexibility in void formation, with a maintained necessary strength, permitting diverse lightening measures to be promoted by way of a reduction of plate body.
Another aspect of the invention to achieve the object is a molded resin plate formed with internal voids, comprising a single mold made of a resin body increased in a size, and blind holes formed in the resin body, as the size is increased, the blind holes each respectively having an external communication hole opening at an outside of the mold. According to this aspect, there is provided a molded resin plate with internal voids in which internal voids of desirable dimensions and configurations can be formed at desirable locations by using pressures introduced from external communication holes to control balancing points between pressures of a resin body having an increasing size and those in internal voids formed by the size increase, with an increased flexibility in void formation, with a maintained necessary strength, permitting diverse lightening measures to be promoted by way of a reduction of plate body.